A man who San Mateo County prosecutors say left behind DNA evidence at a crime scene more than 25 years ago appeared in court Tuesday on cold-case charges that he raped and murdered a teenage girl.

John William Kelley, 49, of Placerville (El Dorado County) appeared in San Mateo County Superior Court where he was ordered to return Sept. 21 to enter pleas.

In court papers, prosecutors allege that Kelley picked up Annette Thur, 17, of Ben Lomond (Santa Cruz County), who was hitchhiking home after midnight one morning in 1986 from a party in nearby Boulder Creek.

Authorities say Kelley took Thur to his Ben Lomond home, where he either suffocated or strangled her before dumping her body down an embankment along Skyline Boulevard in unincorporated San Mateo County. Thur's body was discovered by a hiker just hours after the killer left the scene, authorities said.

But the crime went unsolved for 2 1/2 decades until cold-case investigators with the San Mateo County Sheriff's Office entered DNA evidence into a national database and turned up a match.

Detectives questioned Kelley at his Placerville home Aug. 15 and arrested him after the interview.

Kelley's attorney, Tom Kelley (no relation), said that his client would plead not guilty and that the validity of the aging DNA evidence would be challenged.

"This case is not what it appears to be," Tom Kelley said, noting police had told the victim's mother that her daughter had died from a cocaine overdose. At the time, police made statements that suggested Thur's fellow partiers had probably dumped her along the roadside.

"I guarantee this case will have a lot of twists and turns," the defense lawyer said. "It was a long time ago."

In September 1986 - three months before the Thur killing - Kelley was sentenced to 90 days in a Santa Clara County jail for statutory rape, records show.

Kelley's DNA was on file after he was convicted in Eureka in 1995 of forcible rape, for which he received a six-year prison term.

Kelley had been out of jail and registered as a sex offender for more than 10 years before investigators visited him this month.